Medicinal plants are an important therapeutic aid for various ailments. Scientific experiments on the antimicrobial properties of plant components were first documented in the late 19th century.[1] In India, from ancient times, different parts of medicinal plants have been used to cure specific ailments. Today, there is widespread interest in drugs derived from plants. This interest primarily stems from the belief that green medicine is safe and dependable, compared with costly synthetic drugs that have adverse effects. Natural antimicrobials can be derived from plants, animal tissues, or microorganisms.[2] The shortcomings of the drugs available today, propel the discovery of new pharmacotherapeutic agents in medicinal plants.[3] To determine the potential and promote the use of herbal medicine, it is essential to intensify the study of medicinal plants that find place in folklore.[4],[5] In this study, some selected plants of Saurashtra region, India, were screened for potential antibacterial activity.

A total of 20 plants were screened. [Table - 1] Different parts of the plants were collected, air dried, and powdered in a homogeniser, and 10 g of each plant was used for aqueous and ethanol extraction. The aqueous extraction was done in distilled water for 6 hours at slow heat. The extract was concentrated to 1/5th of the original volume for antimicrobial assay. For ethanol extraction, the sample was extracted in ethanol kept on a rotary shaker overnight. The filtrate was collected and centrifuged at 5000 rpm. The extract was concentrated to 1/5th of the original volume and used for antimicrobial assay.

The antibacterial activity of ethanol extracts of various plants screened are shown in [Table - 2]. The ethanol extracts of B. diffusa, A. squamosa, H. sabdariffa , and A. racemosus showed the least antibacterial activity, while E. officinalis, C. wightii, F. religiosa, P. hysterophorus, F. benghalensis, F. tesila, F. racemosa, D. indica, C. papaya, O. sanctum, A. graveolens, P. granatum, and Z. nummularia showed maximum antibacterial activity. The ethanol extracts of P. hysterophorus, F. tesila, D. indica, and Z. nummularia inhibited the growth of 9 strains. P. hysterophorus showed maximum activity against B. cereus . F. tesila was highly active against S. agalactiae , while D. indica and Z. nummularia were highly active against S. agalactiae and E. aereogenes, respectively. These plant extracts were also compared with standard antibiotics, piperacillin and gentamicin. Aqueous extracts showed less activity than ethanol extracts possibly because i) the same active substances were present in water extracts, but in low concentrations ii) active substances were soluble in organic solvents and, therefore, not present in water extracts as also suggested by de Boer et al [8].The antibacterial action of the extracts is more pronounced on Gram positive than on Gram negative bacteria, and these findings correlate to the observations of previous screenings[5],[9] of medicinal plants for antibacterial activity. From the above results, it can be concluded that the plant B. diffusa did not exhibit any antibacterial property and P. vulgaris, E. aerogenes, and E. coli were the most resistant bacterial strains investigated. Plant extracts have great potential as antimicrobial compounds, especially in the treatment of infectious diseases caused by resistant microorganisms.